The present application relates generally to operation of internal combustion engines, and more particularly but not exclusively to raising temperatures of an exhaust gas stream produced by an internal combustion engine for, by way of non-limiting example, facilitating regeneration of one or more components of an aftertreatment system.
Modern internal combustion engines must meet stringent emissions standards, including a maximum amount of nitrogen oxides (NOx) that may be emitted. Many engines now utilize aftertreatment systems to reduce engine-out emissions to regulatory levels before release to the atmosphere. Aftertreatment systems often include multiple components, including particulate filters, oxidation catalysts, NOx adsorbers, NOx reduction catalysts, three-way catalysts, four-way catalysts, and can further include multiple components of the same type at various locations along the aftertreatment system flowpath. One well known way of removing oxides of nitrogen (NOx) from engine exhaust is Selective Catalyst Reduction (SCR). In this system a catalyst is used to facilitate a reaction between NOx molecules and a reductant to convert the NOx into common atmospheric gasses.
Over time, one or more components of the aftertreatment system can become masked by deposits of certain constituents of the exhaust gas, which can decrease the efficiency of such components and result in an undesired increase in emissions. More particularly, and by way of non-limiting example, SCR systems can become masked with sulfur deposits which affect their efficiency in removing oxides of nitrogen (NOx) from engine exhaust, particularly in situations where engines are operated with high sulfur fuels (e.g., having a sulfur content of greater than 50 ppm) and on low temperature duty cycles. Accordingly, there is a demand for further improvements in this area of technology.